James Bellinger, February 2007 1

DCOPS AnalysisDCOPS AnalysisDCOPS AnalysisDCOPS Analysis

James N. Bellinger

University of Wisconsin at Madison

9-February-2007

DCOPS Data from MTCC2

James Bellinger, February 2007 2

Simple AnalysisSimple AnalysisSimple AnalysisSimple Analysis

This is not a substitute for using COCOA, which is what we intend for the final

determination of position.

Finding the absolute Z positions requires use of the Z-sensors.

James Bellinger, February 2007 3

DCOPS SensorDCOPS SensorDCOPS SensorDCOPS Sensor

CCD 3: RPhi

CCD 1: RPhi

CCD 2: Z

CCD 4: Z

The L

ine has 10 DC

OP

S, w

ith a laser at each end

James Bellinger, February 2007 4

Piecing together lines for Z Piecing together lines for Z measurementsmeasurements

• Disk bending tilts the lasers• Field-off: laser offscale one way by #8 of 10• Field-on: laser offscale other direction• By #9 the laser beam has vanished• Have to piece together incomplete lines

James Bellinger, February 2007 5

RPhi measurementsRPhi measurements

• Disk bending has little effect: beam reaches far side• Field off• Field on• RPhi is the crucial direction for momentum

measurements

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Analysis ApproachAnalysis ApproachAnalysis ApproachAnalysis Approach

• Fit the measured positions with a straight line. The resulting residuals are independent of the laser direction and show the variation from an “average position” level.

• Residuals can be refit, and the resulting new residuals will be the same as the old ones. I rely on that when piecing Z-measuring lines together.

James Bellinger, February 2007 7

Field-OFF ME+2/SLM1 Field-OFF ME+2/SLM1 Z measurementsZ measurements

• CCD2=+

• CCD4=*

• PG=o

The positions areconsistent with theshimming.The data was takenover several weeks, and is clearly stable.Photogrammetry isin good agreement

ME+21/10

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Field-ON ME+2/SLM1 Field-ON ME+2/SLM1 Z measurementsZ measurements

• CCD2=+

• CCD4=*

• Change from field OFF is consistent with disk bending estimates

• Measurements are stable

James Bellinger, February 2007 9

Quality notesQuality notes

• CCD2 profiles were somewhat shadowed in the 6’th and 7’th DCOPS, so the quality of the profiles’ fits are poorer. It shows in the distribution of residuals, and in the RMS of the following slide.

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Z measurement stabilityZ measurement stability

Station CCD2 CCD40 92 511 78 522 30 353 41 264 88 655 28 1266 261 1047 44 118 140 269 155 31

CCD2 = 96 micronsCCD4 = 53 microns

Measurements weretaken over 3 weeks

Field is OFF

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Rphi residuals: Field ONRphi residuals: Field ON

• Laser 1= +

• Laser 2= *

• This is the direction critical for momentum measurement

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Rphi measurement stabilityRphi measurement stability

Station TP1 Laser TP4 LaserTP1 10 401/2/O 10 1061/2/I 5 492/3/O 11 492/3/I 12 322/20/I 19 222/20/O 13 1131/10/I 22 221/10/O - 20TP4 33 26

Laser 1 = 15 micronsLaser 2 = 48 microns

Measured over weeks

Field is ON, CCD1

James Bellinger, February 2007 13

Rphi residuals and Rphi residuals and photogrammetryphotogrammetry

• Laser 1 OFF= +

• Laser 2 OFF= *

• PG = o

• Agreement with photogrammetry is usually good

• Laser 1 and 2 data are consistent

James Bellinger, February 2007 14

Rphi residuals Field OFF and ONRphi residuals Field OFF and ON

• Laser 1 OFF= +

• Laser 2 OFF= *

• Laser 1 ON = o

• Laser 2 ON = x

• CCD 3 data

• Shifts are noticeable

• Measurements are stable

James Bellinger, February 2007 15

Change in RPhi from OFF to ONChange in RPhi from OFF to ON

• Laser 1 = *• Laser 2 = o• The endpoints of each

distribution on the previous slide were corrected to be 0 before subtracting to get these, so the endpoints have change=0 by construction.

• This is a relative measure of the Rphi change when the field turns on, using CCD3

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SummarySummary

• The DCOPS system works and can locate misaligned chambers

• COCOA should work

• Disk bending is consistent with predictions

• The ability to adjust the laser direction would help

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Auxilliary MaterialAuxilliary Material

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Quality studiesQuality studiesQuality studiesQuality studies

• Although after solving the previous two problems I had reasonable-looking results for the fits, the histograms were plagued with fliers.• Hand scanning showed which CCDs were

consistently bad (and I then always excluded these) and which “events” had unusually bad profiles. This can be made automatic later. So far it looks as though the absolute signal size [available] and signal to background [not available in MTCC data] are the most useful quantities.

James Bellinger, February 2007 19

Piecing together partial linesPiecing together partial lines

1. Fit one side’s data: 7 DCOPS worth

2. Fit the other side’s data: 7 DCOPS worth (there was sometimes more, but I was being conservative)

3. Fit the difference between the residuals of the above two fits in the overlap region.

4. Use this to extrapolate into the right-hand side’s data from the left and calculate residuals from this “virtual laser.”

5. Using the left side’s residuals and the extrapolated residuals, fit this set to a line and find the residuals from that fit.

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Scanning for both lasers onScanning for both lasers on